The effect of non-uniform transmission filters on the axial and extraaxial responses of aberrated optical systems is studied. The axial Strehl ratio (SR) is increased by varying the filter transmission function and the extra-axial SR by shifting the filter position along the axis of the optical system. It is shown that a filter which optimizes the axial SR can also improve the extra-axial SR. There are some positions of the filter for which the total results are improved. These positions are explained from the lack of radial symmetry of the wave aberration. The filters which improve the SR are also studied in terms of energy transmission. © 1989 Taylor & Francis Group, LLC.